This invention relates to the connection of tubular members. The invention has particular application to the connections of subsea tubular members such as wellheads and pipelines. It is a requirement of such connections that they cannot be released by pressure to which they are exposed. Furthermore, it is a requirement that the connection be releasable when there is a requirement to disconnect the tubular members.
Many prior art arrangements have used connectors which rely upon the angle of taper between locking dogs or a ring and an actuator mechanism in such a way there is a self-locking taper. This creates problems in that it relies upon the coefficient of friction between the engaged members remaining the same and the application of a lubricant may so change this coefficient that the taper does not remain self-locking.
U.S. Pat. No. 3,321,217 describes a subsea connector which is remotely actuated and relies upon a wedge ring to force locking dogs into engagement with grooves to complete the connection and also relies on a self-locking taper between the two to maintain the locked position.
U.S. Pat. No. 4,057,267 discloses a pipe connector which is said to be particularly useful for connecting underwater riser sections and includes remotely actuated hydraulic means for moving a locking dog radially inwardly into a locked position and a remotely actuated hydraulic means for moving a locking dog radially inwardly into a locked position and a remotely actuated hydraulic means for moving a cam into position to lock the dogs and their actuator in a locked position.
U.S. Pat. No. 4,222,592 discloses another type of connector for underwater members which includes an over-the-center toggle mechanism which is remotely actuated to move locking dogs into engagement with their grooves and the past center position of the toggle mechanism resists unlatching of the dogs from their grooves.
Examples of collet type connectors for the connection of tubular members are described in, for example, U.S. Pat. Nos. 4,165,470, 4,049,297 and 4,074,912.
U.S Pat. No. 4,265,891 describes a tubular connector in which first and second tubular members have external engaging means. The members can be latched by a latching means which can be releasably retained by a locking means.
U.S. Pat. No. 4,557,508 describes a tubular connector in which a collet type segmented engaging element has projections which can engage grooves in the adjacent ends of two tubular members to be connected. The engaging means is urged into engagement with the grooves by means of an actuator ring which wedges the engaging means into tight latching engagement with the grooves on the tubular members. The actuating ring is held in position by a split ring.